Safety pressure relief device and method for making the same

ABSTRACT

A vacuum support for use with a safety pressure relief rupture member. A vacuum support disk includes a convex side and a concave side with the convex side being positioned against a concave side of the rupture disk which also includes convex and concave sides. A arc-shaped slit, centered with respect to the vacuum support disk, is formed therethrough and permits fluid communication between either side of the vacuum support disk. A pair of opposed substantially parallel disk edges define opposte sides of the slit. The edges are urged against one another when the pressure on the concave side of the vacuum support disk is lower than the pressure on the convex side of the rupture disk thereby supporting the rupture disk.

This is a continuation of prior copending application Ser. No. 018,206,filed Feb. 24, 1987, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to safety pressure relief devices andmore particularly, but not by way of limitation, to a safety pressurerelief device designed for positive rupture in one direction at apre-determined pressure differential to protect a pressure vessel. Theinvention also relates to methods for making such safety pressure reliefdevices.

2. Description of the Prior Art

A variety of safety pressure relief devices of the rupture disk typehave been developed. Generally, these devices include a rupture disksupported between a pair of complementary supporting members or flangeswhich are in turn connected to a relief connection in a vessel or systemcontaining fluid pressure.

Safety pressure relief devices of the rupture disk type are often usedin environments having elevated temperatures, alternating pressure andvacuum and corrosive conditions. When such disks are exposed toalternating internal and external pressures the central portion of thedisk fluctuates responsive to the pressure diferentials thus stressingthe disk and ultimately leading to disk rupture at a pressuredifferential other than that for which the disk was designed. As usedherein, the term "positive pressure" refers to a condition in whichpressure in the vessel is greater than pressure on the other side of thesafety pressure relief device while the term "reverse pressure" refersto a condition in which the vessel pressure is less than the pressure onthe other side of the presure relief device.

In order to stablize the rupture disk against fluctuating in response toalternating internal and external pressure differentials, a vacuumsupport is clamped between the complementary flanges which contain therupture disk with the vacuum support being positioned internally of therupture disk. In some constructions, a sealing member is interposedbetween the vacuum support and the rupture disk. Thus, the vacuumsupport prevents fluctuation of the rupture disk or seal when a vacuumoccurs in the pressure vessel in which the safety pressure relief deviceis installed. Examples of such supports are shown in U.S. Pats. No.2,523,068 to Simpson et al. and U.S. Pat. No. 2,953,279 to Coffman.

A problem occurs with such prior art vacuum supports. In manyapplications, the vacuum support must be thick enough to support therupture disk or seal in the presence of a high reverse pressure. At thesame time, the vacuum support must also be able to open completely uponthe occurrence of the positive pressure at which the rupture disk isdesigned to open. When the rupture disk is designed to open at arelatively low positive internal pressure, the vacuum support may be sothick that full opening of the assembly at the pre-determined positivepressure is prevented thus restricting flow.

Prior art vacuum supports typically include a plurality of petalsdefined by radial cuts in the vacuum support. Lugs are welded onto thevacuum support adjacent the cuts in order to maintain the structuralintegrity of the vacuum support in the presence of reverse pressurewhile a sufficient pre-determined positive pressure opens the petalsupon bursting of the rupture disk. In the past, it has been necessary todesign vacuum supports of varying thicknesses dependent upon the levelof reverse pressure the vacuum support must withstand. Moreover, somedesign parameters are not achieveable using prior art vacuum supports.In other words, when it is desired to have the vacuum support withstanda very high reverse pressure while opening in the presence of a very lowpositive pressure, the vacuum support may be so thick that rupture ofthe disk at the positive pressure may not occur.

In addition to the foregoing problems, the lugs which are spot weldedonto the prior art vacuum supports constitute surface irregularitiesupon which process in the vessel may accumulate. When such process iscorrosive, especially in the presence of high temperatures, theeffective life of the vacuum support is reduced.

It is important that when the internal pressure in the vessel reachesthe pre-determined positive pressure at which the rupture disk opens,the vacuum support opens completely and fully while at the same timeretaining parts so that vacuum support fragments are not sent downstreamof the safety pressure relief device.

By the present invention, a safety pressure relief device of the rupturedisk type is provided which includes a vacuum support which is simplyand easily constructed, which opens completely and positively at lowrupture disk pressures while supporting the rupture disk in the presenceof a high reverse pressure, which is useable with rupture disks having awide range of reverse pressure and rupture pressure ratings, and whichopens positively and completely without fragmenting when internal vesselpressure exceeds rupture disk opening pressure.

SUMMARY OF THE INVENTION

The present invention relates to a vacuum support for use with a safetypressure relief rupture member. The vacuum support comprises a diskhaving a generally convex upper side and a generally concave lower sideand a slit formed therethrough. An upper disk edge defines first, agenerally upper side of the slit and a lower disk edge defines second, agenerally lower side of the slit. The slit edges are pressed togetherwith the lower disk edge supporting that portion of the disk generallyabove the slit responsive to downward force applied to the disk.

Another aspect of the invention comprises a method for making a vacuumsupport for use in a safety pressure relief device of the rupturabletype. The method includes the steps of forming a disk having a convexupper side and a concave lower side. Thereafter a slit is formed throughthe disk which divides the same into generally lower and upper portions.The slit is narrow enough relative to the disk thickness to close andprevent the upper portion from collapsing downwardly into the lowerportion responsive to downward pressure applied to the upper portion.

It is, therefore, an object of the present invention to provide animproved safety pressure relief device of the rupturable type.

It is a further object of the present invention to provide such a safetypressure relief device in which the rupture disk is supported in thepresence of high reverse pressure and which opens positively andcompletely at a pre-determined positive low pressure.

It is another object of the present invention to provide such a safetypressure relief device which includes a vacuum support that is useableover a wide range of rupture disk reverse pressure and positive pressureratings.

It is yet another object of the present invention to provide such asafety pressure relief device which is easily constructed and whichincorporates fewer parts than those in the prior art.

It is still another object of the invention to provide such a safetypressure relief device having a vacuum support which is formed ofthinner material than those in the prior art.

It is another object of the invention to provide such a safety pressurerelief device which opens positively and completely at a pre-determinedpositive pressure and which does not fragment upon opening.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectioned perspective view of a safety pressurerelief device constructed in accordance with the instant invention withportions thereof broken away.

FIG. 2 is an exploded perspective view of the safety pressure reliefdevice of FIG. 1.

FIG. 3 is an enlarged partial cross-sectional view of a portion of thesafety pressure relief device of FIG. 1.

FIG. 4 is a top plan view of the vacuum support of the safety pressurerelief device of FIG. 1.

FIG. 5 is a view taken along line 5--5 in FIG. 4.

FIG. 6 is an enlarged view of a portion of FIG. 5.

FIG. 7 is a cross-sectional view of the safety pressure relief device ofFIG. 1.

FIG. 8 is a view similar to FIG. 7 after rupture of the safety pressurerelief device.

FIG. 9 is a cross-sectional view of a second embodiment of a vacuumsupport constructed in accordance with the instant invention.

FIG. 10 is an enlarged view of a portion of FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Indicated generally at 10 is structure incorporating a safety pressurerelief device constructed in accordance with the instant invention. Abase flange 12 is threaded or otherwise suitably connected to a pipe ortubular member 14 which serves as the relieving outlet for a pressurevessel to be protected. Indicated generally at 16 is a safety pressurerelief device constructed in accordance with the instant invention.Device 16 includes a vacuum support 18, a sealing member 20, and arupture member or disk 22. Device 16 is installed between base flange 12and a hold-down flange 24. The hold-down flange is generally providedwith threads 26 or other suitable means of connecting piping (not shown)to vent fluids away from the vessel area when required. Flanges 12, 24are bolted together via bolts, like bolt 28, as shown. Safety pressurerelief device 16 serves as a gasket between flanges 12, 24 to provide asealed connection for the pressure vessel.

Turning attention now to FIG. 2, rupture disk 22 includes an upperconvex side 30 and a lower concave side (not visible in FIG. 2). Rupturemember 22 includes an anchoring flange 32, such also being viewable inFIG. 7. A plurality of slots, like slot 34, extend radially outwardlyfrom a solid central portion 36. A hole, like hole 38 is drilled orpunched at the upper end of each of the slots, like slot 34, to preventstress concentrations at the upper slot ends.

Rupture disk 22 is constructed to positively burst when the pressure intubular member 14 exceeds the pressure on the other side of the pressurerelief device by a pre-determined amount. The pre-determined pressure atwhich such bursting occurs for any diameter of the safety pressurerelief device may be selected by varying metal thickness, tensilestrength of the metal being considered, and varying the length of theslots, like slot 34. For example, the longer the slots, the closer theirproximity at central portion 36 of rupture disk 22 and the smaller thearea will be between the slots to resist the internal pressure of thevessel.

Sealing member 20 is made to conform with the shape of rupture disk 22or must be of sufficient flexibility to assume such shape when assembledas part of the unit. Since the function of the sealing member is simplyto prevent leakage through device 16 and to prevent corrosion of rupturedisk 22, it may be made from a wide variety of materials. The selectionof a material as a sealing member should be made individually for eachinstallation with caution taken to assure the protection of rupture disk22 from corrosion. It should be appreciated that it is known to combinesealing member 20 and rupture disk 22 into a single rupture disk whichalso seals to prevent leakage.

Vacuum support 18 is shown in more detail in FIGS. 4-6 and attention isdirected thereto for a description of the vacuum support structure.Vacuum support 18 includes a circular disk 39 having a generally convexupper side 40 and a generally concave lower side 42. A substantiallyhorizontal (as viewed in FIG. 5) slit 44 is formed through vacuumsupport 18 and defines an arc centered about an axis designated bydot-dash line 46. One end of slit 44 terminates in a hole 45 to relievestress concentrations. Axis 46 also comprises the central axis for disk39. Slit 44 divides disk 39 into an upper disk portion 48 and a lowerdisk portion 50.

An anchoring flange 52 is formed about the radially outer circumferenceof disk 39 and provides a means for anchoring device 16 between flanges12, 24 when vacuum support 18, sealing member 20, and rupture disk 22are nested together as shown in FIGS. 1 and 7. A flat arcuate portion 54comprises the radially outermost edge of disk 39 and assists inanchoring the vacuum support between flanges 12, 24.

Slit 44 is defined by an first, upper edge 56 and a second, lower edge58, such being referred to herein as an upper disk edge and a lower diskedge, respectively. The disk edges are substantially parallel to oneanother and in the instant embodiment of the invention each defines anangle of substantially 60° with respect to axis 46. A second axis 60 isshown in FIG. 6, such being normal to axis 46 and parallel with arcuateportion 54. A third axis 62 is parallel to disk edges 56, 58. Thus, inthe instant embodiment of the invention, the angle between axes 60, 62,designated by arc 64 (hereinafter angle 64) is substantially 30°. It hasbeen found that the safety pressure relief device of the invention willsuccessfully operate, as will hereinafter be described in more detail,when disk edges 56, 58 are oriented so that angle 64 is within the rangeof 0°-45°.

A second slit 66 is formed through disk 39 and is symmetrical withrespect with slit 44. Like slit 44, slit 66 includes a hole 68 at oneend thereof to relieve stress concentrations. Although not visible inthe drawings, slit 66 includes first and second edges, like edges 56,58, which are parallel to one another and which, like edges 56, 58, forman angle of substantially 60° with respect to axis 46. Each of slits 44,66 have one end which terminates in holes 45, 68 and another end 70, 72,respectively. That portion of the disk between holes 45, 68 is referredto herein as a vacuum support hinge portion and that portion of the diskbetween ends 70, 72 is referred to herein as a vacuum supportpositioning portion. The vacuum support positioning portion maintainsupper portion 48 in alignment with lower portion 50 when vacuum support18, sealing member 20, and rupture disk 22 are nested together forassembly as shown in FIGS. 1 and 7.

In operation, vacuum support 18, sealing member 20, and rupture disk 22are assembled between flanges 12, 24 as previously described and asshown in FIGS. 1 and 7. The pressure on the vessel to be protectedoperates on the concave side of sealing member 20 through slits 44, 66and holes 45, 68 in vacuum support 18. When properly assembled, sealingmember 20 nests in the concave side of rupture disk 22 so that pressuretransmitted to sealing member 20 is exerted by the sealing memberagainst the concave side of rupture disk 22.

When pressure in tubular member 14 falls below the presure on the convexside of rupture disk 22, vacuum support 18 prevents substantial flexingof rupture disk 22 and sealing member 20 in response to fluctuatingpresure. In response to the lower presure internal of tubular member 14,a downward force is exerted by seal 20 against vacuum support 18 thuspressing upper edge 56 of slit 44 against lower edge 58 and likewisepressing the upper and lower edges of slit 66 together so that thevacuum support assumes the configuration of FIG. 3. Due to the domeshape of vacuum support 18 and the abutment of the slit edges flatagainst one another, vacuum support 18 is able to maintain theconfiguration of FIG. 3 even in the presence of very high reversepressures. This is so even when the vacuum support is made from thinnermaterial than used in prior art vacuum supports.

Pressure interior of tubular member 14 which is greater than pressure onthe other side of safety device 16 acts against sealing member 20 on thelower side of rupture disk 22. When such pressure reaches the level atwhich disk 22 is designed to burst, the metal between the holes (likehole 38 in the upper portion of disk 22) separates, except for one setof holes as shown in FIG. 8, thus permitting the disk to open as shown.When rupture disk 22 opens, the pressure causes seal 20 to tear andvacuum support 18 to hinge open as shown in FIG. 8. As can be seen, thematerial between slit ends 70, 72 breaks thus permitting the vacuumsupport to hinge open as shown in FIG. 8.

Vacuum support 18 may be designed to assure that it will withstand areverse pressure differential of a selected amount without collapsing.The strength of the vacuum support when exposed to reverse pressure isdetermined by the radial distance between axis 46 and slits 44, 66;angle 64; the thickness of the disk; and the width of the slits, i.e.,for slit 44, the distance between edges 56, 58. The degree of positivepressure which the vacuum support will withstand is a function of thethickness of the disk and the distance between ends 70, 72.

It is to be appreciated that the slit width will vary dependent upon thethickness of the disk from which the vacuum support is made and thedistance between ends 70, 72 will vary dependent upon the diameter ofthe rupture disk which in turn is dependent upon the diameter of therupture disk with which the vacuum support is used.

It can be seen that the structure of the vacuum support of the inventionis able to withstand high reverse pressures because of the manner inwhich the slit closes with lower disk portion 50 supporting upper diskportion 48 as shown in FIG. 3. This improved vacuum support structurewithstands higher reverse pressures than previous vacuum supports andcan be formed from thinner material than previous vacuum supports. Thus,the vacuum support of the invention withstands very high reversepressures while at the same time, because of the thin material fromwhich the vacuum support disk is made, opens positively and completelyat low positive pressures. Thus, unlike prior art vacuum supports, for agiven rupture disk size, the vacuum support of the instant invention maybe used over a wide range of positive and reverse pressure ratings forits associated rupture disk.

Indicated generally at 74 in FIGS. 9 and 10 is a second embodiment of avacuum support constructed in accordance with the instant invention.Vacuum support 74 includes a pair of symmetrical slits, one of which isslit 76, formed through a domeshaped portion of the vacuum supportsimilar to vacuum support 18. Vacuum support 74 includes a substantiallyplanar radial flange 78 which is used to mount the vacuum support in atype of mounting flange different from flanges 12, 24 in FIG. 1.Otherwise, vacuum support 74 functions in the same manner (with anassociated rupture disk and seal, each of which have planar flangessimilar to flange 78) as the embodiment of FIG. 1. It is to beappreciated that means other than those disclosed herein for mounting avacuum support constructed in accordance with the instant invention maybe utilized without departing the scope of the invention.

Turning now to FIG. 6, included therein is a laser 80. When makingvacuum support 18, laser 80 is used to form slits 44, 66 with a laserlight beam being aligned with axis 62 thereby forming the slit edges 56,58 at an angle dependent upon the orientation of laser 80. Laser 80provides precision control in selecting both the angle of edges 56, 58and the width of slit 44 thus enabling the vacuum support to beprecisely designed to withstand a given amount of reverse pressure. Avacuum support so constructed includes fewer parts than vacuum supportsof the prior art which typically have lugs spot welded thereto adjacentcuts which are formed through disk 39 in order to withstand reversepressure to a preselected amount.

It is to be appreciated that additions and modifications may be made tothe embodiments disclosed herein without departing from the spirit ofthe invention which is defined in the following claims.

We claim:
 1. A vacuum support for using with a safety pressure reliefrupture member comprising:a disk having a convex side and a concaveside, and defining a slit through said disk sides having a pair ofopposing ends, wherein said disk includes:an upper disk portiongenerally above said slit, said upper disk portion being positionableagainst one side of the rupture member for supporting the rupture memberwhen the pressure on said concave side of said disk is lower than thepressure on the other side of the rupture member; a lower disk portiongenerally below said slit; a vacuum support hinge defined between saidopposing slit ends for swinging movement of said upper disk portionrelative to said lower disk portion; and means for supporting said upperdisk portion against swinging movement on said vacuum support hinge in adirection away from the rupture member in the presence of reversepressure, said supporting means consisting solely of a pair of opposedsubstantially planar disk edges defining opposite sides of said slit,said edges being urged substantially flushly against one another whenthe pressure on said concave side of said disk is lower than thepressure on the other side of the rupture member.
 2. The vacuum supportof claim 1 wherein a distance between said disk edges is less than athickness of said disk.
 3. The vacuum support of claim 1 wherein saiddisk defines a second slit through said disk sides.
 4. The vacuumsupport of claim 3 wherein said slits have a second pair of opposingends defining a vacuum support positioning portion therebetween.
 5. Thevacuum support of claim 4 wherein said vacuum support positioningportion is substantially shorter than said vacuum support hinge.
 6. Thevacuum support of claim 1 wherein said slit defines an arc.
 7. Thevacuum support of claim 6 wherein said disk defines a second slitthrough said disk sides, said second slit defining an arc such that saidarcs together define an arc greater than 270°.
 8. The vacuum support ofclaim 6 wherein said convex side, said concave side, and said arc arecentered on a common axis.
 9. The vacuum support of claim 8 wherein saiddisk edges form an angle of between 45° to 90° with said axis.
 10. Thevacuum support of claim 9 wherein said angle is substantially 60°.
 11. Avacuum support comprising:a disk having a generally convex upper sideand a generally concave lower side, said disk having a slit formedtherethrough and further including:a vacuum support hinge defined by apair of opposing ends of said slit, said vacuum support hinge allowingswinging movement of that portion of said disk generally above said slitrelative to that portion of said disk generally below said slit; asubstantially planar upper disk edge defining a generally upper side ofsaid slit; and a substantially planar lower disk edge defining agenerally lower side of said slit, said disk edges being pressedsubstantially flushly together by downward force applied to said diskwith said lower edge solely supporting that portion of said diskgenerally above said slit against downward swinging motion.
 12. Thevacuum support of claim 11 wherein said slit is substantiallyhorizontal.
 13. The vacuum support of claim 11 wherein said upper andlower disk edges are substantially parallel to one another.
 14. Thevacuum support of claim 11 wherein a distance between said upper andlower disk edges is less than a thickness of said disk.
 15. The vacuumsupport of claim 11 wherein said disk defines a second slit through saiddisk sides.
 16. The vacuum support of claim 15 wherein said slits have asecond pair of opposing ends defining a vacuum support positioningportion therebetween.
 17. The vacuum support of claim 16 wherein saidvacuum support positioning portion is substantially shorter than saidvacuum support hinge.
 18. The vacuum support of claim 11 wherein saidslit defines an arc.
 19. The vacuum support of claim 18 wherein saiddisk defines a second slit through said disk sides, said second slitdefining an arc such that said arcs together define an arc greater than270°.
 20. The vacuum support of claim 18 wherein said convex side, saidconcave side, and said arc are centered on a common axis.
 21. The vacuumsupport of claim 20 wherein said disk edges form an angle of between 45°to 90° with said axis.
 22. The vacuum support of claim 21 wherein saidangle is substantially 60°.
 23. A vacuum support comprising:a diskhaving a generally convex upper side and a generally concave lower side,and defining a slit through said disk sides having a pair of opposingslit ends, wherein said disk includes:an upper disk portion locatedgenerally above said slit; a lower disk portion located generally belowsaid slit; a vacuum support hinge defined between said opposing slitends for swinging movement of said upper disk portion relative to saidlower disk portion; means for preventing said upper disk portion fromswinging downwardly through said lower disk portion, said meansconsisting solely of opposed substantially planar upper and lower diskedges defining generally upper and lower sides, respectively, of saidslit, said edges substantially flushly abutting one another responsiveto downward pressure applied to said upper disk portion.
 24. The vacuumsupport of claim 23 wherein the opposed substantially planar upper andlower disk edges define opposite sides of said slit.
 25. The vacuumsupport of claim 23 wherein a distance between said upper and lower diskedges is less than a thickness of said disk.
 26. The vacuum support ofclaim 23 wherein said disk defines a second slit through said disksides.
 27. The vacuum support of claim 26 wherein said slits have asecond pair of opposing ends defining a vacuum support positioningportion therebetween.
 28. The vacuum support of claim 27 wherein saidvacuum support positioning portion is substantially shorter than saidvacuum support hinge.
 29. The vacuum support of claim 23 wherein saidslit defines an arc.
 30. The vacuum support of claim 29 wherein saiddisk defines a second slit through said disk sides, said second slitdefining an arc such that said arcs together define an arc greater than270°.
 31. The vacuum support of claim 29 wherein said convex side, saidconcave side, and said arc are centered on a common axis.
 32. The vacuumsupport of claim 31 wherein said disk edges form an angle of between 45°to 90° with said axis.
 33. The vacuum support of claim 32 wherein saidangle is substantially 60°.
 34. A vacuum support for use with a safetypressure relief rupture member comprising:a disk having a convex sideand a concave side, and defining a slit through said disk sides having apair of opposing ends, wherein said disk includes:a pair of opposed diskedges which define first and second sides of said slit; an upper diskportion positioned above said first side of said slit and positionableagainst one side of the rupture member for supporting the rupture memberwhen the pressure on said concave side of said disk is lower than thepressure on the other side of the rupture member; a lower disk portionpositioned below said second side of said slit; a vacuum support hingedefined between said opposing slit ends for swinging movement of saidupper disk portion relative to said lower disk portion; and means forsupporting said upper disk portion against swinging movement on saidvacuum support hinge in a direction away from the rupture member in thepresence of reverse pressure, said supporting means consisting solely ofsaid pair of opposed disk edges, said edges being urged into contactwith one another when the pressure on said concave side of said disk islower than the pressure on the other side of the rupture member.
 35. Thevacuum support of claim 34 wherein each of said opposed disk edges issubstantially planar.
 36. The vacuum support of claim 34 wherein adistance between said disk edges is less than a thickness of said disk.37. The vacuum support of claim 34 wherein said disk defines a secondslit through said disk sides.
 38. The vacuum support of claim 37 whereinsaid first and second slits have a second pair of opposing ends defininga vacuum support positioning portion therebetween.
 39. The vacuumsupport of claim 38 wherein said vacuum support positioning portion issubstantially shorter than said vacuum support hinge.
 40. The vacuumsupport of claim 34 wherein said slit defines an arc.
 41. The vacuumsupport of claim 40 wherein said disk defines a second slit through saiddisk sides, said second slit defining an arc such that said arcstogether define an arc greater than 270°.
 42. The vacuum support ofclaim 40 wherein said convex side, said concave side, and said arc arecentered on a common axis.
 43. The vacuum support of claim 42 whereinsaid disk edges form an angle between 45° to 90° with said axis.
 44. Thevacuum support of claim 43 wherein said angle is substantially 60°.